I agree with Beefcake. - 2 Bros black series in carbon. Looks great, sounds great, as good of a performance bump as you'll get with any of them, which honestly isn't much. They do knock about 8 pounds off compared to the stock can - that thing is a boat anchor!
The 2 Bros install is easy - 1/2 hour, good hardware AND it's the only slip on that uses the stock cover plate to cover the pipe section from the cat back to the can. I'm very happy with mine - I debated between it and the Yoshi, price and the cover plate sold me.
i agree with the two bros i also have one and i love it! i dont think you could go wrong with any of with any of these pipes i have also read great things about the akrapovic also
The exhaust for my FZ8 bike were purchased from motorcycle-exhaust-shop24.com > Yamaha > FZ8, they guys that work there are incredible, know every product they sell in and out and are willing to spend time with you figuring out what's best for your application.
The Mivv pipe is nice! I'd have to 2nd that on the Damoto exhaust, It's a really good value. I've got the Jisu pipe and I'm very happy with it (tho it's a totally diff look than the Mivv)